What type of bike?

If you are going to ride trails, a CRF150F or an older XR100 may work for you...depending on height. I would probably forget about racing until you get more experience. Trails would be a good place to learn to ride. As your skills improve, you may try tracks in a year or so...by then you will probably want to upgrade to another bike.

How much have you ridden your friend's CR85? How did you do on it?

If you found the CR85 difficult to manage or frustrating then you might want to stick with a four stroke, they are a lot more forgiving to beginners. I normally wouldn't recommend a two stroke for a beginner but if you did all right on it then they are a good option.

I would NOT recommend the CRF150F for you. The 150F is what many would consider a girls bike (electric start) and you might not enjoy the ridicule that you might encounter from your friends. Instead I would recommend the Honda CRF150RE. Note that the "E" stands for expert, not "electric start" like some other bikes. The RE model gets you a higher performance engine, more suspension travel (very important for racing) about 50 pounds lighter, larger wheels and two more inches of seat height.

Seat height could be a big issue for you at 16. At 5'8" you are already a bit tall for a 32" seat height, but the 38" height of a full size bike would be a stretch for you and not at all good for a beginner. The CRF150Re has a seat height of 34" which will be perfect for you right now and will still be OK if you grow a bit in the next couple of years.

If you want to consider a two stroke then I would recommend a Kawasaki KX100. These bikes are about 2 inches taller than the CR85 you are familiar with and about the same weight.

Rod

If electric start makes a bike a "girls bike"...I ride with alot of A and B class "girls". The best way to avoid ridicule is to become a better rider. How can someone make fun of you if you can outride them? A guy that I ride with has a daughter that is 20 years old that can outride any of my beginner friends...her bike has pink all over it...do you think anybody gives her grief? No, because she is a better rider.

At 5'8", height would likely be an issue with the taller 150R. I doubt this kid will have any of the suggested bikes in a couple of years. If he rides at all, he will want to upgrade before then.

I have a buddy with a KTM 300 2 stroke (not girls bike) that is electric start. I have seen several guys on a CRF150F, you might bore of it after a little while though as it is very tame. Depends on your comfort level if you want a F or an R.

I normally give conservative advise to beginners. Once they learn how to ride, they can make their own decisions on what to buy. This guy will be 18 in 2 years...if he rides at all, I doubt he will keep a 150F or 150R. To me, it makes alot more sense to buy a cheap, used 150F or XR100, beat the hell out of it learning to ride, sell it for a very small loss, then upgrade to a better bike you wont wreck every ride..because you are a better rider.

I am the minority in my group of riders...almost everyone has electric start...from WR450s to KTM300EXCs and 450EXCs. My older WR426 and XR400 are both kick start, but I am used to it.

When you are old like me then electric start is a really nice feature! I wish I had the "happy button". The next bike I buy will certainly have one.

When you are 16 years old it is a completely different set of peer pressure issues that need to be dealt with. I know several families that bought their son an electric start bike which basically resulted in the kid never riding again. i suppose it might be different if the kid wanted to ride verses the dad wanting the kid to ride but facing the ridicule of your peers is a very real issue to consider.

There were other reasons that I recommended the RE over the F as well. If he grows any more then CRF150F will be too small. Having the center of gravity too high along with a limited suspension travel is just asking for a trip over the handlebars. While electric start can be convenient it also adds a lot of weight, which becomes even more significant on the smaller bikes.

Rod

Tough call. Important question up there; "how did you do on the 85?" and what terrain were you riding it in? Are you likely to grow taller soon (how tall are your parents, brothers, sisters, etc?) You at the upper end of height for a kx100 and a crf150r, and almost tall enough for a full size bike. My kids got their first full size bikes (mx bikes) at your height/age, but they already had several years of riding experience. And don't discount that experience, as there is a fairly steep learning curve to deal with. You want an easy-to-ride bike to start with, for sure. Again, how did you do on the '85, truthfully. Many here can really help you with this.

I agree the question about terrain is key. Most beginners at any age can ride just about any bike [their size] around in a flat field..as long as you can operate a clutch and gears. My beginner friends rode my YZ400F around a flat grassy field for a few hours with no problem. The same riders were in way over their heads riding a tame XR400 on beginner to intermediate level trails a few weeks later.